Priority is claimed with respect to German Application No. 198 51 979.6-16 filed in Germany on Nov. 11, 1998, the disclosure of which is incorporated herein by reference:
The invention relates to a temperature detector for a vehicle seat with a seat heating system and/or seat ventilation system and to a vehicle seat with an integrated temperature detector of this kind. In a known seat heating system for a motor vehicle seat (DE 197 03 516 C1), the temperature detector, which can be obtained commercially as a spherical or disc-shaped element made from a temperature-dependent resistor material, is arranged in the lower area of the back cushion, in the pressure distribution layer of the latter, and is connected to the input of a control unit, which is connected on the output side to electric heating coils of the seat heating system. The control unit controls the on time of the seat heating system in accordance with a specified control algorithm as a function of the temperature at the surface of the back cushion, measured by the temperature detector.
Such commercially available temperature detectors allow only the local temperature to be detected and this is subject to severe fluctuations, especially when the seat is occupied, and can vary widely from one point to another. This leads to distortion of the actual temperature value fed to the temperature-regulating system and to correspondingly deficient temperature regulation which does not meet high requirements on the comfort of the seat.
The object on which the invention is based is to provide a temperature detector of the type stated at the outset which reliably performs more accurate temperature measurement for regulation purposes and does this close to the surface of the seat while eliminating purely local temperature peaks.
According to the invention, the object is achieved by means of a flat, extended heat absorption surface.
The temperature detector according to the invention has the advantage of detecting the temperature at the surface of the seat over a wide area, thus minimizing interfering effects such as the temperature detector being acted upon on one side, the occupant side. It is thereby possible to measure the temperature as close as possible to the user of the seat, thus coming significantly closer to the goal of temperature regulation, namely to keep the temperature of the seat constant in the same range as the skin temperature.
Advantageous embodiments of the temperature detector according to the invention with expedient refinements and developments of the invention will become apparent from the further claims.
According to an advantageous embodiment of the invention, the heat absorption surface is formed by a thin, flexible layer of very good thermal conductivity into which a temperature sensor, e.g. a PTC or NTC resistor, in button or disc form is firmly embedded. The advantage of this flat construction resides in the fact that the temperature detector does not leave a visible imprint on the surface of the seat and there is therefore no problem in arranging the temperature detector directly under the cushion cover. The layer of good thermal conductivity can advantageously be produced by means of an aluminium foil but can also be produced from aluminium powder. An outside diameter of about 40 mm is sufficient to achieve the desired advantages.
According to an advantageous embodiment of the invention, the heat-conducting layer is perforated or in the form of a latticework structure. The air permeability thus obtained for the large-area heat absorption surface has the advantage of minimizing condensation and evaporation of moisture on the heat absorption surface and temperature fluctuations caused thereby.
In the case of a vehicle seat which is fitted with a temperature detector as described above, an advantageous embodiment of the invention is obtained if the temperature detector, the heat absorption surface of which is provided on one side with a layer of good thermal conductivity, is integrated in such a way into the cushion that the thermal insulating layer faces away from the cushion cover, thereby ensuring that the temperature detector is shielded on the ventilation side.
If the seat heating system has an electric heating mat, which is generally arranged under the cushion cover, then, according to another embodiment of the invention, the temperature detector is an integral part of the heating mat.
According to an advantageous embodiment of the invention, a temperature-regulating device forming part of the seat heating system is supplied with a desired value for the seat surface temperature, is connected on the input side to the temperature detector and an external detector, which is arranged on the vehicle and detects the outside temperature, and, on the output side, to the seat heating system. The temperature-regulating device regulates the surface temperature of the seat in accordance with the specified desired value and corrects the desired value as a function of the temperature value measured by the external detector. These design measures contribute to better adjustment of the seat climate to the heat sensitivity of the occupant, thus ensuring that any manual interventions that he makes in the seat-climate setting are kept to a minimum. By adapting the desired temperature value to the outside temperature, e.g. by setting the desired value for the seat surface temperature to 35xc2x0 C. in summer, when the outside temperature is above 20xc2x0 C., and to 36xc2x0 C. in the cold part of the year, when the outside temperature is below 20xc2x0 C., allowance is made for the differences in human temperature sensitivity according to the season.